1. Field of the Invention
The present invention relates to an inner-rotor motor.
2. Description of the Related Art
There has been a demand for an increase in power of inner-rotor DC motors. Inner-rotor DC motors are used in applications such as vacuum cleaners, washing machines, and food processors. Vacuum cleaners or the like particularly require a motor with a high rotation rate, and it is therefore difficult to improve specifications (e.g., high speed rotation, high torque, etc.) of the motor of the vacuum cleaner or the like because of a generation of heat in an armature thereof. DC motors have been increasingly reduced in size because of market demand, and it is considered to be primarily important to provide small-sized DC motors which have specifications equivalent to those of existing larger DC motors.
JP-A 2-174528 discloses a permanent magnet rotor 1 in which blades 6 are arranged while holes are defined in a housing 7 of a motor in which the permanent magnet rotor 1 is included.
JP-A 1-110035 discloses a brushless motor in which fins 30 are arranged to cause winds to pass from cooling air inlets 28 arranged at an axially upper end to cooling air outlets 29 arranged at an axially lower end.
However, the techniques described in JP-A 2-174528 and JP-A 1-110035 do not overcome a problem in that it is difficult to force air into the motor when atmospheric pressure has become increased in the vicinity of an armature.